Dynamo-electric machine rotating by electromagnetic induction such as it acts in linear electric motors

ABSTRACT

The present invention relates to a dynamo-electric machine rotating by electromagnetic induction such as it acts on linear electric motors. It possesses a ring-shaped rotor ( 1 ) and an inductance coil stator ( 2 ) interacting at least with a part of said rotor ( 1 ).

CROSS REFERENCE TO RELATED APPLICATION

The present application is the national stage under 35 U.S.C. 371 ofPCT/IT98/00155, filed Jun. 11, 1998.

TECHNICAL FIELD

The present invention relates to a dynamo-electric machine rotating byelectromagnetic induction such as it acts in linear electric motors.

As is well known, the linear electric motor can be thought of as beingderived from a normal asynchronous motor by longitudinally sectioningand rectifying both the stator and the rotor.

The operating principle is based on the generation of a magnetic fieldwhich varies spatially with uniform rectilinear motion instead of withrotatory motion as occurs in the normal asynchronous motor.

In the asynchronous linear motor, the inductor generates currents on thearmature and the interaction between such currents and the inductingfield gives rise to an inducting force directed longitudinally.

It is already known that in linear motors there is no dimensionalconstraint between inductor and armature.

The present invention aims to overcome also the constraint of theextended shape which is the basis for the linear motor.

An example of a linear motor is disclosed in the patent DE 2217466A. Thepatent discloses an induction motor comprising a disc of electricalconductor and a 3-element stator, each element comprising a core andwindings. Another example of a linear motor can be found in GB1282485 Athat discloses a ring-shaped rotor carried by fan blades, which extendradially outward from a hub mounted on a central shaft. In any of thesedocuments , the rotor is mounted on a central shaft. An example of amotor having a rotor in the form of a hoop can be found in the documentGB2103768A. In this document the stator and the hoop are ofsemi-cylindrical section and are thus semi-tiroidal in shape.

DISCLOSURE OF INVENTION

The main object of the present invention is to realise a dynamo-electricmachine, i.e. one operating both as a motor and as a generator, whichemploys the technology of the linear electric motor to allowrealisations not effected so far on a rotating machine.

The invention, as it is characterised by the claims that follow, solvesthe problem of providing a dynamo-electric machine rotating byelectromagnetic induction such as it acts in linear electric motors,which from a general standpoint is characterized in that it possesses aring-shaped rotor in the form of a flattened annulus, being fitted withat least one circumferential rail engaged with sliding guides, and aninductance coil stator interacting at least with one part of said rotor.

In other words, the present invention allows to realise a linearelectric machine which, functioning for instance as a motor, has alinear armature closed in a loop at its ends to serve as a rotor, and arelated stator, at least one fixed inductor, interacting with saidarmature at least on a part of its said loop.

One of the advantages obtained through the present invention essentiallyconsists of the fact that, when said rotor is mounted for rotation onsliding guides, the structure of the machine is essentially hollow, andinside it may be housed various contrivances for the direct integrationof the machine itself with systems for the utilisation of mechanical orelectrical energy, or both, depending on whether the dynamo-electricmachine functions as a motor or as a generator, or as both at subsequenttimes.

Another advantage is represented by the fact that the rotor of thismachine can have a moment of inertia which can be easily modified byvarying its radius. Hence it is possible to modify the torque producedfor equal amounts of power supplied to the induction coil, in case ofoperation as a motor, with the consequent optimisation in the variousapplications. In addition, the need for gears or other reduction andindirect transmission means normally required to adapt the torqueproduced by the motors to the user is eliminated. In the absence of suchreduction and transmission organs, the cost normally required for theutilisation of the mechanical energy is reduced, thanks to a lowernumber of necessary components, and the final mechanical efficiency isalso increased.

With the use of a variable number of modular inductors, the power of themachine can be modified consequently. The invention can have varioustypes of power supply and efficiency, depending on whether it functionsas a motor or as a generator.

Yet another advantage of the invention is to allow large efficienciessimply by increasing the scale factor of the embodiments.

Thanks to the simplicity of construction, provided by the modularstructure of the machine, its reliability is high, and its maintenanceis made easier and does not require the intervention of particularlyspecialised personnel.

Given its flat and essentially compact structure, the machine accordingto the invention is easily and conveniently integrated in all itsapplications, in particular in those having internal spaces withparticular volumes and shapes.

Overall, with respect to prior art electric machines, improvements areobtained in all mechanical characteristics, in adaptability, indimensional and mechanical terms for the applications, in reliabilityand in servicing.

DESCRIPTION OF THE DRAWINGS

Additional characteristics and advantages of the present invention shallbecome more readily apparent from the detailed description that follows,of preferred. embodiments shown purely by way of non limitingindications in the accompanying drawings wherein:

FIG. 1 shows a schematic perspective view of major components of themachine according to the invention.

FIG. 2 shows a schematic perspective view of major components of themachine in a second embodiment of the invention.

FIG. 3 shows a schematic side view of major components of the machine ina third embodiment of the invention.

FIG. 4 shows a schematic perspective view, partially sectioned off, ofthe machine according to the invention in a first application thereof.

FIG. 5 shows a schematic perspective view of the machine according tothe invention in a second application thereof

FIG. 6 shows a schematic perspective view, partially sectioned off, ofthe machine according to the invention in a third application thereof

FIG. 7 shows a plan schematic view of the machine according to theinvention with central support rotor and multiple inductors.

FIGS. 8 through 11 show schematic side views of the machine with centralsupport rotor in constructive variations.

FIGS. 12 and 13 show schematic plan views of the machine in twodifferent servo-mechanisms.

FIGS. 14 through 18 show schematic plan views of the machine indifferent construction and application variations fitted with slidingguides.

FIGS. 19 and 20 show schematic perspective views of two versions,complete with casing of the machine according to the invention, for theradially internal and. respectively, external transmission.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

In accordance with the present invention, in the figures identical orsimilar parts of the machine according to the invention are indicatedwith the same numbers. With reference to FIG. 1, the number 1 indicatesa rotor, the number 2 a stator, the number 3 sliding guides for therotation of the rotor 1 and, alternatively thereto, the number 4indicates a central support for the same rotor 1.

The rotor 1 is obtained by closing in a loop the armature of a linearmotor. The rotor 1 therefore is ring-shaped, like an annulus, and it haspreferably flattened shape. In a first embodiment thereof, shown in FIG.1, the rotor comprises permanent magnets, generically indicated as 10and 11, arranged in succession with their N, S polarities opposing oneanother in orderly fashion. Other embodiments of the rotor are shown anddescribed hereafter with reference to FIGS. 2 and 3.

In a first embodiment, the rotor 1 is splined onto the shaft 12 of themachine by means of the central support 4, comprising a hub 40 andmultiple spokes, indicated generically as 41. The spokes 41 together mayconstitute a single disk (not shown). FIG. 1 shows three spokes 41. Someapplications of the rotor with central support are shown and describedhereafter.

A second embodiment, alternatively to the central support 4 with centralshaft, can comprise the sliding guides 3 for the rotation of the rotor1. The sliding guides 3 can be formed essentially by roller 30 fastenedand revolving adjacent to the rotor (as shown in the subsequentfigures), each roller 30 being provided with a circumferential groove31. In the circumferential groove 31 of the rollers 30 is received aprojection 13, 14 formed on all the outer and, respectively, innerperiphery of the rotor. One or the other of the projections 13 and 14serves as a guiding rail for the rotation of the rotor 1. Therefore,with this embodiment the machine according to the invention isinternally hollow, allowing for multifarious applications, whereof someare shown and described below.

The stator 2 is an inductor interacting at least with one part of therotor 1. It comprises an inductance coil 20 and an electromagnetic core21. The electromagnetic 21 presents an air gap 22. With respect to therotor 1, the stator 2 is fastened in such a way that the rotor 1 crossesthrough the air gap 22, so that the end facets of the electromagneticcore 21 face the permanent magnets 10, 11 of the rotor 1.

Alternatively, the stator can comprise, as shown hereafter, at least aninductance coil and a closed magnetic core with flux concatenated withthe rotor.

With reference to the FIG. 2, in a second embodiment, a ring-shapedrotor 5 comprises, instead of the orderly succession of permanentmagnets, a succession or self-induction turns generically indicated as50. The stator is represented by three inductance coils crossed byrespective current phases.

With reference to FIG. 3, in a third embodiment a ring-shaped rotor 6comprises a crown 60 made of material able to be magnetised, forinstance soft iron, sandwiched between two opposite crowns 61, 62 madeof a material not subject to magnetisation, such as an aluminum alloy.In this third embodiment of the machine according to the invention, thestator is schematically shown as an inductor with three opposed poles25, 25 powered in pairs with a respective phase of the power supply lineA, B and C. The interaction between the fields of the poles integralwith the stator inductor and the currents induced in the metallic rotor6 produces, peripherally thereto, an accelerating force represented bythe tangential arrow F in FIG. 3.

FIG. 4 schematically shows an application of the machine according tothe invention, functioning as a motor in a washing machine 7. The shaft12, whereon is splined the central support 4 of the rotor 1, is integralwith the central agitator (not shown) of the washing machine 7, insideits tank 70. This application of the machine according to the inventionhighlights the advantages described above, among them the absence ofsome transmission organs, such as bearings, pulleys, transmission belt,the increase in efficiency, the reduction of the size of the appliance,the easier maintenance. The control unit of the motor according to theinvention instead is similar to that of the traditional motor andtherefore is not described.

FIG. 5 schematically shows another application of the machine accordingto the invention, to the driving wheel 80 of a bicycle 8. The rotor 1 isintegral with the wheel 80, whilst the central support 4 of the rotorreplaces the spokes of the wheel. The stator 2 is connected to a bufferbattery 81, which is charged when the machine according to the inventionfunctions as a generator, i.e. when muscle power is used, in downhillstretches of roads and when braking. The motor starts operating whenhigh speeds are desired, or uphill or when, on a flat stretch of road,the rider wishes to proceed without effort. The control unit is shownschematically as 82. Immediately apparent are the advantages of theinvention with respect to the other current systems of electric drivefor bicycles, and like them the invention can use a solar cell batterycharger.

FIG. 6 schematically shows yet another application of the machineaccording to the invention, as a driving device for aport vehicles. Anelectric motor is constructed with a shaft 12 having four stages 9 andfour inductor modules 2 for each stage. The motor is placed inside acasing, in oil bath, provided with a cooling circuit 90.

FIGS. 7 through 11 show, by way of example, some versions of centralsupport rotor for electric machines according to the invention. Thestator may have the desired number of inductors 2 (FIG. 7), whichencompass the rotor 1 with their air gap (FIG. 8). The rotor 1 (FIG. 9)can present a metallic ring 15 able to be magnetised and an inductor 23,external to the rotor 1. The flux of the inductor 23 is concatenatedwith the rotor 1 through the ring 15. The rotor 1 can have its moment ofinertia increased by a flywheel mass 16 (FIG. 10) or it may have itsinduction enhanced by a pair of opposed inductors 24 (FIG. 11).

FIGS. 12 and 13 show, by way of example, some versions of centralsupport rotor for electric machines according to the invention appliedto servo-controls. The stator 2 interacts with a rotor limited in itsextension to an annulus portion 17. To this annulus portion 17 isintegral an arm connected to a pair of gears 32 (FIG. 12) or to a wheeland worm screw pair 33 (FIG. 13).

FIGS. 14 through 18 show, by way of example, some versions of rotor withsliding guides for electric machines according to the invention. Thestator can have the desired number of inductors 2 (FIG. 14), whichencompass the rotor 1 with their air gap (FIG. 8). The cavity inside therotor can be used for the integration of the machine according to theinvention with the desired utilisation. The rotor 1 (FIG. 15) canpresent internal sliding guides 3 and internal stator 2 and it can beprovided with external mechanical transmission means, shownschematically as 34. The rotor 1 (FIG. 16) can present external slidingguides 3 and external stator 2 and it can be provided with internalmechanical transmission means, shown schematically as 34. FIGS. 17 and18 schematically show two examples of the application shown,respectively, in FIGS. 15 and 16. In FIG. 17, the rotor presentsinternal sliding guides 3, four internal inductors 2 and on its outerperiphery teeth for engagement with a chain 35. In FIG. 18, the rotor 1presents, though they are not shown, external sliding guides, anexternal inductor 2 and on its inner periphery means 36 for connectionwith a drum 37.

Lastly, FIGS. 19 and 20 show a single stage machine according to thepresent invention, enclosed in ahollow cylinder casing 38, 39, andprovided with internal connecting means for transmission, such as aflange 42 (FIG. 19) and with external transmission means such as a crowngear 43 (FIG. 20). The compactness of the machine according to theinvention is further shown.

The invention thus conceived can be subject to numerous modificationsand variations, without thereby departing from the scope of the sameinnovative concept. Moreover, all components can be replaced withtechnically equivalent elements. In practice, modifications and/orimprovements are possible without thereby departing from the scope ofthe claims that follow.

What is claimed is:
 1. Dynamo-electric machine rotating byelectromagnetic induction such as it acts in linear electric motors,characterised in that it possesses a ring-shaped rotor (1) in the formof a flattened annulus, being fitted with at least one circumferentialrail (13, 14) engaged with guides, and an inductance coil stator (2)interacting at least with one part of said rotor (1), and furthercharacterised in that said circumferential rail (13) is external to thestator (2).
 2. Electromagnetic machine according to claim 1,characterised in that said stator (2) comprises at least one inductancecoil (20) and an electromagnetic core (21) provided with an air gap (22)crossed by said rotor (1).
 3. Electromagnetic machine according to claim1, characterised in that said stator (2) comprises at least oneinductance coil (23) and a closed magnetic core with flux concatenatedwith said rotor (1).
 4. Electromagnetic machine according to claim 1,characterised in that said ring-shaped rotor (1) comprises a successionof permanent magnets (10, 11) with polarities opposed in orderlyfashion.
 5. Electromagnetic machine according to claim 1, characterisedin that said ring-shaped rotor (5) comprises a succession ofself-induction turns (50).
 6. Dynamo-electric machine rotating byelectromagnetic induction such as it acts in linear electric motors,characterised in that it possesses a ring-shaped rotor (1) in the formof a flattened annulus, being fitted with at least one circumferentialrail (13, 14) engaged with sliding guides, and an inductance coil stator(2) interacting at least with one part of said rotor (1), and furthercharacterised in that said ring-shaped rotor (5) comprises a crown madeof a material able to be magnetised (60) sandwiched between two oppositecrowns (61, 62) of a material not subject to magnetisation. 7.Electromagnetic machine according to claim 6, characterised in that saidmaterial able to be magnetised is soft iron and said material notsubject to magnetisation is an aluminum alloy.